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The Mystery of Bioluminescent Bays Uncovered!


The light up water… is it magic? The mystery of Bioluminescent Bays Uncovered

Information verified and provided by Robert Charley, PhD, Microbiology

There is nothing more spectacular than witnessing a rare natural phenomenon where a tranquil body of water is illuminated by an intoxicating neon-blue glow in the darkness of the night. Visitors from around the world are fascinated by the mysterious sensation of bioluminescence, and why certain bodies of water are capable of lighting up and what is the cause of this enchanting wonder of nature.


Bays which are known for this phenomenon, commonly called sea sparkle, are scientifically known as bioluminescent bays. Bioluminescencecomes from biomeaning lifeand luminmeaning light.  Puerto Rico is home to three of these bays: “La Parguerain Lajas in the South West, “Mosquito Bayin Vieques, and “La Laguna Grandein Farjado. Mosquito Bay is the brightest and most well known bioluminescent bay in the world, emitting a powerful blue-green colour which illuminates the water at night time.


Bioluminescence is a biochemical reaction which naturally occurs in an organisms biological makeup. It involves the oxidation of the light emitting pigment luciferin, catalysed by the enzyme luciferase, which results in the emission of light.

Mosquito Bay is inhabited by up to 720,000 single-celled bioluminescent dinoflagellates, more commonly known as marine plankton, per gallon of water. The dinoflagellates are half-plant, half-animal organisms which emit a flash of bluish light at when they become agitated or disturbed, causing the water to light up and sparkle. Because of the high concentration of their population, enough light can be created by the organisms to see clearly and even read a book!



The dinoflagellates found in Mosquito Bay use bioluminescence as a natural defence mechanism to scare away predators, as the predators themselves may be spotted by creatures higher in the food-chain due to the illumination of the water. Tours are available for visitors to the area on a flat electric pontoon boat, which is eco-friendly and extremely quiet, to minimise disturbance to the natural habitat.


Bioluminescence was first recorded in the Caribbean during the colonial period. Spanish explorers tried to close off Mosquito Bay from the rest of the ocean, as they feared the phenomenon and tried to prevent it; they believed it to be the work of the devil!


The process occurs most widely in marine environments: there are many creatures, such as the firefly squid, which feature it naturally; others, glow themselves because they feed on bioluminescent organisms. On land, bioluminescence occurs in fireflies, glow-worms, some insect larvae, and specific species of worms and spiders.




Bioluminescent bodies of water are rare, but in addition to the tree bays in Puerto Rico, the following four locations offer exquisite insight to witness bioluminescence up close:

Halong Bay, Vietnam

Waitomo, New Zealand

Springbrook Park, Australia

San Juan Island, Washington, U.S


“The most incredible thing to me is to think that when you see a shimmering bay or witness bioluminescence yourself by swimming or standing in the shallow water, is that it is the result of billions of these microorganisms producing an enzyme-driven reaction. – Robert Charley, PhD, Microbiology

Lauren Charley

Lauren Charley

Writer at aLookingGlass
Lauren graduated with an Honours B.A. in Media Studies from the University of Western Ontario in Canada. She has worked as a feature magazine writer, where many of her stories pertained to events, people, activities, and places in popular tourist destinations.

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